The invention relates to a method and a device for dividing a flow of bulk material into a plurality of sub-flows.
When processing flowable bulk materials, particularly, waste glass fragments, the problem arises of uniformly dividing-up a flow of such material into two or more smaller flows of the material. This is often necessary for the further processing of the material, for example, sorting the bulk material in terms of size, color, weight, etc.
A conveying and distributing plant for bulk materials such as sand, chemical granulates or the like is known from U.S. Pat. No. 2,674,381 wherein a feed flow of such materials is supplied to a horizontal conveying region, which is coupled to a vibrator and which also executes vertical movements. The vibrator advances the bulk material towards filler-openings in the conveying region, or to a conveyor trough, into which the bulk material falls insofar as the filler opening is not already filled with bulk material. Above the filler-openings, the bulk material builds up into a small hill which is mechanically smoothed should it become too large in order to avoid reactions with the feed flow for example. In the ideal case, the un-discharged bulk material above the filler-openings is then passed onto the next filler opening so that it can be re-subjected to the processing action. The danger of blockage can only be avoided with the aid of a complex mechanical arrangement.
U.S. Pat. No. 2,758,752 describes a plant, with the aid of which granulate or flowable solids from a single supply source can be distributed to a plurality of processing stations. This plant comprises a vertical shaft having a plurality of inclined, downwardly extending bifurcations along its length. These bifurcations each end in a funnel. The funnel is provided with blocking mechanisms. As soon as a funnel is full of material, it automatically blocks the bifurcation and thereby stops any further supply of material. This is intended to ensure that each of the processing stations is either kept fully operational under optimum loading conditions, or can remain switched off. Complicated blocking mechanisms are required for the correct functioning of the plant.
Another method, which is also relatively complex, is described in WO 94/24029. Here, a chute whose inclination is greater than the maximum expected is angle of slope of the bulk material is provided for dividing a flow of bulk material into a plurality of sub-flows. Filler-openings are disposed in the chute for a plurality of stockpiling containers provided below the chute for the respective sub-flows. The filler-openings for the stockpiling containers are arranged in such a manner that reactions with the preceding stockpiling container can be precluded by virtue of the closure behavior. However, a disadvantage of this method and of this device is that a plant of this type is subject to failure due to its complex construction. Despite this complexity, consistent and uniform distribution of the bulk material flow is still not assured.
Furthermore, it has been shown in practice that methods used for Newtonian fluids are either not usable for bulk materials or can only be implemented with difficulty. The reason for this can be seen in the pseudo-plastic flow behavior of the bulk materials, i.e. a minimum shear force has to be overcome before the flowing motion can commence. This is physically apparent from the angle of slope of an accumulation of bulk material. In addition, the flow properties of bulk materials are dependent on external factors such as the moisture content, surface area and the shape and/or size of the constituents. Overall, the flow behavior of bulk material is non-linear.
In the case of other known systems of division, an alteration in the distribution in one sub-flow usually has an effect upon each or a plurality of the other sub-flows. Due to the non-linear behavior of the flow, these effects can only be anticipated to a limited extent and this thus makes it necessary to take extensive measures in order to effect corrections and maintain a uniform flow of material.
The object of the invention is to provide an arrangement for dividing bulk materials into a plurality of sub-flows thereby allowing a uniform distribution to be obtained without reactive effects, and which is constructed in as simple a manner as possible. This object is achieved by a method in accordance with claim 12 and by a device in accordance with claim 14.
Surprisingly, due to the bulk material being dammed in the form of a vertical column, uniform sub-flows will be branched off from openings in the envelope of the column (pipe) whereby, in each case, just that amount of particulate bulk material is moved out from the main flow as is being carried off in the sub-flow. That is to say, a stable static state is created at each of the openings, this state arising due to the bulk material settling at its angle of repose in the branch pipes. If particles of bulk material should now move out of the open end of the pipe, then in fact, just so many particles then flow in from behind as will allow the static state of a supporting medium deposited at its angle of slope to be recreated.
A vibratory action is used in order to assist the conveyance of the sub-flow in the downstream direction. It is thereby possible to affect the quantity of material being branched into the sub-flow. Additional blocking devices for the individual outlets are not required.
A device of this type is particularly economical if the distributing pipes, the bifurcations and the branch pipes consist of plug-in, synthetic material pipes such as are known from the field of sanitation. For example, conventional waste pipes of the required dimensions can easily be plugged together. If one section of pipe should wear out, a replacement pipe can easily be inserted. Waste pipes of this type can be obtained economically from stock at a building supply house or from specialty suppliers.
In addition to the self-induced vibrations occurring when the plant is in operation, conveyance of the bulk material along the substantially horizontally disposed branch pipes can be assisted or enabled by means of a vibration generator.
In order to permit the distribution to occur at differing floor levels, it is preferred that a plurality of bifurcations be arranged above one another along the distributing pipe. These bifurcated sub-flows disposed one above the other lead, for example, to one of a plurality of downstream, bulk material sorting plants which often require a considerable amount of space and are of limited processing capacity due to their mechanical devices.
A plurality of further processing plants may be provided downstream of the bifurcations on each of the floor levels by arranging for a plurality of distributing pipes to be laid alongside one another so that they are substantially parallel.
In the case of appropriately connected plants having five parallel processing troughs, it is preferred that five distributing pipes be grouped alongside one another in a row and/or that four mutually spaced groups of distributing pipes be arranged in a plane.
If the distributing pipes are supplied with bulk material from a stock-piling container, whereby the container has a V-shaped cross-section perpendicular to the plane formed by the distributing pipes and has elevated sections on the base of the container between the groups of distributing pipes in the longitudinal direction, it will be ensured that each of the mutually parallel distributing pipes will be properly filled without dead zones being created in the stock-piling container.